1. Field of the Invention
The present invention relates to flow through capacitors, and more particularly to flow through capacitors for removing ionic substances from charged fluids.
2. Description of the Prior Art
Flow through capacitors have been developed to separate materials from fluid streams, such as salt from water. For example, Andleman U.S. Pat. Nos. 5,192,432, 5,196,115, 5,200,068, 5,360,540, 5,415,768, 5,547,581, 5,620,597, and U.S. Pat. No. 5,538,611 to Toshiro Otowa describe flow through capacitor systems which filters polluted and brackish water between alternating electrodes of activated carbon (the capacitors). When voltage is applied, salts, nitrates, totally dissolved solids and other adulterants in the water are attracted to the high surface area carbon material. Solids develop on the electrodes, and thus the process must be stopped to remove the contaminants as concentrated liquid. This is accomplished by short-circuiting of the electrodes.
This method has been taught as a better process for water desalinization than traditional systems like reverse osmosis, which passes through contaminants such as nitrates, promotes bacterial growth and wastes one or more gallons of water for every one it purifies. Further, ion exchange systems, also widely used, generate pollution and use strong acids, bases and salts to regenerate the resin.
Deionized water is employed in many commercial applications, such as semiconductor and chrome-plating plants, automobile factories, beverage production, and steel processing. Further, systems are contemplated in homes units, businesses, manufacturing and municipal facilities, and other applications which can recycle their water output, cutting costs and protecting the environment.
Of course, a prime objective flow through capacitor technology entails the desalinization of sea water at a reasonable cost, providing an inexhaustible supply of usable water to regions in need. Presently, advanced research is underway using new materials including carbon nanotubes. However, nanotechnology has yet to become an affordable and fully understood area.
Nonetheless, the water demands of the Third World are immediate. Two-thirds of the world population do not have access to clean water. Most disease in the developing world is water-relatedxe2x80x94more than 5 million people a year die of easily preventable waterborne diseases such as diarrhea, dysentery and cholera.
Plainly stated, potable water will be the most valuable commodity in the future. The world""s population will double in the 50 to 90 years. Per capita water consumption increases while the supply deteriorates. 80% of the world""s population lives within 200 miles of a coastline where water is available but not potable or suitable for agriculture. 70% of the ground water is brackish. 85% of all illness is associated with unsafe drinking water.
Therefore, it is needed in the world a low cost, safe, and efficient system and process to desalinate water, or to remove other substances from a material, as is needed.
The above-discussed and other problems and deficiencies of the prior art are overcome or alleviated by the several methods and apparatus of the present invention for removing ionic substances from fluids, such as removing salt from water. A flow through capacitor system is provided having one or more movable electrodes. A movable electrode may be in the form of a movable belt structure or a roller. The system further includes at least one subsystem for removing ions that accumulate at the one or more movable electrodes.
In one embodiment, one movable electrode is positioned and configured proximate to a second stationary electrode, to allow passage of a fluid therethrough. Upon application of a voltage across the electrodes, ions of a certain charge are attracted to the electrode of the opposite charge. For example, in desalinization of water, chlorine ions are attracted to the positive electrode, and sodium ions are attracted to the negative electrode. In the example, where the movable electrode is the negative electrode, sodium ions in a solid or solution may be removed from the movable negative electrode by a subsystem for removing ions. To remove the chlorine ions, the system may be short circuited. This may be particularly desirable wherein chlorine forms rapidly as a gas and evolves from the positive electrode (i.e., at a rate much higher than removal of sodium ions). The removal may be on an as-needed basis, or systematically, for example in a rapidly alternating manner.
In another embodiment, a pair of movable electrodes are positioned and configured proximate one another to allow passage of a fluid therethrough. Upon application of a voltage across the electrodes, ions of a certain charge are attracted to the electrode of the opposite charge. For example, in desalinization of water, chlorine ions are attracted to the positive electrode, and sodium ions are attracted to the negative electrode. Chlorine ions in a gaseous form (e.g., Cl2) may be removed from the movable negative electrode by a first subsystem for removing ions. Sodium ions in a solid or solution may be removed from the movable positive electrode by a second subsystem for removing ions. Alternatively, chlorine ions may remain dissolved in a highly concentrated brackish that is removed.
The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.